Congenital Agenesis of the Corpus Callosum (ACC) is a birth defect which is often associated with mental retardation, but which also occurs in neurologically asymptomatic individuals with normal IQ. For the latter group, the neural defect is often undiagnosed despite mild cognitive and psychosocial impairments. These children often have difficulties in subjects like math and science, may have poor social and interpersonal skills. ACC children have few friends, are relatively naive regarding the implications of social interactions, are the target of teasing by peers (sometimes resulting in conflict) and have a poor sense of humor. When ACC is unrecognized these deficits prove perplexing to parents, teachers, and physicians. Even when ACC is diagnosed by MRI scan (usually fortuitously), little is currently known which could inform parents and teachers about the cognitive and psychosocial prognosis of these individuals. It is the aim of this research to study a group of 10 to 15 subjects, 8 to 20 year olds with ACC demonstrated by MRI scan. Subjects will be of normal intelligence (FSIQ is greater than 85), native-English speaking, and attending regular schools. Subjects with a history of encephalopathy (head trauma, greater than two seizures, psychopathology or taking psychoactive medication) will be excluded. MRI scans will be reviewed on an individual basis for evidence of other CNS pathology. The radiologist will request permission to refer the subject to the study. Subjects will be assessed on an extensive test battery which includes assessment of intelligence, educational achievement, interhemispheric transfer of complex visual, auditory, and sensorimotor information, complex novel problem solving, complex memory encoding, personality and social/interpersonal awareness. It is the intent of this research to develop a sufficiently detailed description of the characteristics of individual with ACC such that the existence of ACC might be detected in others who exhibit unexplained and puzzling learning or behavioral deficits, and to guide the development of educational and psychosocial remedial or compensatory programs. The hypothesis is that both the cognitive and psychosocial difficulties which seem to accompany ACC are related to deficient complex problem solving and encoding of complex information in memory, which is due, in turn, to a reduced availability of a large, bihemispheric poor of cortical processing modules in the absence of a corpus callosum. A better understanding of the cognitive abilities and disabilities of individuals with ACC will further the understanding of the contribution to human cognition of the intercerebral commissures, particularly the corpus callosum.